As the availability of liquid fuels dwindles, those supplies that remain will be increasingly allocated to uses for which there are no readily available substitutes -- such as powering aircraft and ships. Electric power for land vehicles appears to be the most realistic option for the present. Cellulosic biofuels may come to power some share of land transport, but this is still many years away. Electric power is a proven technology and, more importantly, a widespread distribution system for electricity is already here.

If ways of producing hydrogen cheaply and distributing it are ever developed, hydrogen too could provide fuel for vehicles. For the immediate future only electricity, which can come from conservation of existing power production, nuclear power stations and renewable sources, appears to be the most likely power source for land vehicles.

Powering cars and light trucks with electricity does not seem to be an insurmountable problem provided that one is willing to live with their limitations. Progress on improved batteries apparently is being made (although some are skeptical) so that numerous makes and flavors of electric cars and light trucks will likely be coming on the market within the next few years. Developing a battery powered car, however, is one thing, building and marketing hundreds of millions of them, in an era of declining resources, is something else. While the electric car age seems likely to start soon, just how ubiquitous they will become is another question.

The U.S. currently has some 230 million light vehicles in its fleet. If, as seems likely, gasoline and diesel reach unaffordable prices in the next five to ten years, then these vehicles are simply going to be abandoned by the millions as their owners can no longer afford the fuel or be willing to make payments on useless machinery.

For the few that have an alternative fuel vehicle, are very wealthy, or are able to travel in car pools so that many can pay for the gas, the roads are going to have a lot less traffic. In many countries, but particularly here in North America, there is going to be a lot of “stranded investment.” The trillions of dollars that have been spent on cars, trucks, roads, garages, service facilities, parking lots, shopping malls and God know what else, will no longer be of much use without affordable gasoline.

It is easy to imagine office buildings being converted into apartments as the need for office space declines and people seek to live close to places of employment. It is not much of a reach to imagine shopping malls being converted into mixed-use space where apartments, retail and light manufacturing bunched together in what was once retail shopping. Maybe some food growing will take place in space once used for parking lots and all those flat roofs will make excellent places for solar power collectors.

At the rate our natural resources are running out, however, it is doubtful we will be building and selling 100’s of millions of non-fossil fuel cars in the foreseeable future. As our vehicle fleets decline, a lot of underutilized space will become available on our road nets that could be switched to other uses. Again it does not take much imagination to conceive of a lane or two on the interstate system being converted to light rail, high-speed rail or maybe even a maglev. Given the quality and condition and connectivity of the interstate right of ways, it seems like a natural. As soon as the affordable gasoline and diesel dries up, there will be very few users around to object.

Although new rail lines would probably use diesel-electric power initially, the rapidly declining supply and high price of liquid fuel eventually will lead to electrification of at least the main rail lines. In the long run, electric-powered railways coupled with short haul electric trucks, busses and cars, would leave the country with a sustainable transportation system.

There may even be some better ideas around. As long as liquid fuel was cheap, heavy trucks were the preferred way of transporting most goods because of the great flexibility of a truck offers. While light trucks can be easily electrified and are starting to come on the market, heavy trucks are another matter. They simply require too much energy to move large loads for long distances. Batteries might prove capable of powering large trucks for short distances, but certainly not very far.

One idea that surfaced recently was to repower our long-haul trucks with electric engines, some battery capacity, and pantographs to contact overhead wires. By adding overhead wires (catenaries) to a lane or two of our major highways the energy would be available to move trucks for long distances. While this may be expensive to achieve and take many decades to come into widespread use, the idea would appear to have merit – especially when the alternatives are considered.

While electrified rail would be far more efficient at moving goods than electrified trucks, the added flexibility of an electric-powered heavy truck might prove attractive. We already have some 2 million 18-wheelers in America and one would hate to see them scrapped for lack of fuel.

Other large vehicles such as intercity-buses could draw power from overhead lines much as the trolleys and trolley-buses do currently. It is difficult to imagine cars and smaller vehicles extending pantographs many feet into the air to reach power lines, but who knows. Maybe battery recharging lanes for light vehicles will someday be feasible.

When affordable liquid fuels dry up, we are going to be left with a lot of vehicles and their infrastructure that will no longer be of use. With a little imagination, time, and money, much of this stranded investment can become useful again. There certainly will be powerful incentives to introduce whatever works.

In its day, the internal combustion engine was a wonderful device that served us well for over a century. That day, however, will soon be over. It is time to start thinking about and planning for alternatives.